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package alice.util;

import java.io.IOException;
import java.io.InputStream;
import java.io.Reader;

/**
 * This class let a Reader be viewed as an InputStream.
 * The characters read from the given reader are casted to bytes.
 * It works correctly only if the reader use the ASCII-8 enconding
 * (because a char is 2 bytes, but, using the ASCII-8 enconding, the 
 * high byte is always 0, and so the downcasting can be done without
 * losing data) 
 * @author Andrea Bucaletti
 *
 */
public class InputStreamAdapter extends InputStream {
	
	private Reader reader;
	
	public InputStreamAdapter(Reader rd) {
		this.reader = rd;
	}

	@Override
	public int read() throws IOException {
		int x = reader.read();
		
		if(x == -1) return -1;
		else return x & 0xFF;
	}
	
	/**
	 * Since the Reader class doesn't provide the available() method, 
	 * there is no way to know how many characters can be read without
	 * blocking. So we use the ready() method of the Reader, which is true
	 * if the next character can be read without blocking.
	 * So if writer.ready() is true, at least 1 chatacter is available;
	 * otherwise return 0.
	 */
	@Override
	public int available() {
		try { return reader.ready() ? 1 : 0; }
		catch(IOException ex) { return 0; }
	}
	
	@Override
	public void mark(int readLimit) {
		try {
			reader.mark(readLimit);
		}
		catch(IOException ex) {}
	}
	
	@Override
	public boolean markSupported() {
		return reader.markSupported();
	}
	
	@Override
	public void reset() throws IOException {
		reader.reset();
	}
	
	@Override
	public long skip(long n) throws IOException {
		return reader.skip(n);
	}
	
	@Override
	public void close() throws IOException {
		reader.close();
	}
	
}